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<meta name="description" content="漏洞描述在CTFd v2.0.0-v2.2.2的注册过程中，错误的用户名验证会允许攻击者接管任意帐户，前提是用户名已知并且在CTFd实例上启用了电子邮件。要利用此漏洞，必须使用与受害者的用户名相同的用户名进行注册，但在用户名之前和/或之后插入空格。这将使用与受害者相同的用户名注册该帐户。在为新帐户启动密码重置后，由于用户名冲突，CTFd将重置受害者的帐户密码。">
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<meta property="og:description" content="漏洞描述在CTFd v2.0.0-v2.2.2的注册过程中，错误的用户名验证会允许攻击者接管任意帐户，前提是用户名已知并且在CTFd实例上启用了电子邮件。要利用此漏洞，必须使用与受害者的用户名相同的用户名进行注册，但在用户名之前和/或之后插入空格。这将使用与受害者相同的用户名注册该帐户。在为新帐户启动密码重置后，由于用户名冲突，CTFd将重置受害者的帐户密码。">
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<meta name="twitter:description" content="漏洞描述在CTFd v2.0.0-v2.2.2的注册过程中，错误的用户名验证会允许攻击者接管任意帐户，前提是用户名已知并且在CTFd实例上启用了电子邮件。要利用此漏洞，必须使用与受害者的用户名相同的用户名进行注册，但在用户名之前和/或之后插入空格。这将使用与受害者相同的用户名注册该帐户。在为新帐户启动密码重置后，由于用户名冲突，CTFd将重置受害者的帐户密码。">



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          <h1 class="post-title" itemprop="name headline">CVE-2020-7245 账号接管漏洞</h1>
        

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        <h2 id="漏洞描述"><a href="#漏洞描述" class="headerlink" title="漏洞描述"></a>漏洞描述</h2><p>在CTFd v2.0.0-v2.2.2的注册过程中，错误的用户名验证会允许攻击者接管任意帐户，前提是用户名已知并且在CTFd实例上启用了电子邮件。要利用此漏洞，必须使用与受害者的用户名相同的用户名进行注册，但在用户名之前和/或之后插入空格。这将使用与受害者相同的用户名注册该帐户。在为新帐户启动密码重置后，由于用户名冲突，CTFd将重置受害者的帐户密码。</p>
<a id="more"></a>
<h2 id="漏洞分析"><a href="#漏洞分析" class="headerlink" title="漏洞分析"></a>漏洞分析</h2><p>该漏洞主要由注册部分的逻辑产生的<br>查看源码<a href="https://github.com/CTFd/CTFd/blob/fe85fdf1e5561e9f04c1c80c72e894dcd7ea3ad7/CTFd/auth.py#L159" target="_blank" rel="noopener">https://github.com/CTFd/CTFd/blob/fe85fdf1e5561e9f04c1c80c72e894dcd7ea3ad7/CTFd/auth.py#L159</a></p>
<figure class="highlight py"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">def</span> <span class="title">register</span><span class="params">()</span>:</span></span><br><span class="line">    errors = get_errors()</span><br><span class="line">    <span class="keyword">if</span> request.method == <span class="string">"POST"</span>:</span><br><span class="line">        name = request.form[<span class="string">"name"</span>]</span><br><span class="line">        email_address = request.form[<span class="string">"email"</span>]</span><br><span class="line">        password = request.form[<span class="string">"password"</span>]</span><br><span class="line"></span><br><span class="line">        name_len = len(name) == <span class="number">0</span></span><br><span class="line">        names = Users.query.add_columns(<span class="string">"name"</span>, <span class="string">"id"</span>).filter_by(name=name).first()</span><br><span class="line">        emails = (</span><br><span class="line">            Users.query.add_columns(<span class="string">"email"</span>, <span class="string">"id"</span>)</span><br><span class="line">            .filter_by(email=email_address)</span><br><span class="line">            .first()</span><br><span class="line">        )</span><br><span class="line">        pass_short = len(password.strip()) == <span class="number">0</span></span><br><span class="line">        pass_long = len(password) &gt; <span class="number">128</span></span><br><span class="line">        valid_email = validators.validate_email(request.form[<span class="string">"email"</span>])</span><br><span class="line">        team_name_email_check = validators.validate_email(name)</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> <span class="keyword">not</span> valid_email:</span><br><span class="line">            errors.append(<span class="string">"Please enter a valid email address"</span>)</span><br><span class="line">        <span class="keyword">if</span> email.check_email_is_whitelisted(email_address) <span class="keyword">is</span> <span class="literal">False</span>:</span><br><span class="line">            errors.append(</span><br><span class="line">                <span class="string">"Only email addresses under &#123;domains&#125; may register"</span>.format(</span><br><span class="line">                    domains=get_config(<span class="string">"domain_whitelist"</span>)</span><br><span class="line">                )</span><br><span class="line">            )</span><br><span class="line">        <span class="keyword">if</span> names:</span><br><span class="line">            errors.append(<span class="string">"That user name is already taken"</span>)</span><br><span class="line">        <span class="keyword">if</span> team_name_email_check <span class="keyword">is</span> <span class="literal">True</span>:</span><br><span class="line">            errors.append(<span class="string">"Your user name cannot be an email address"</span>)</span><br><span class="line">        <span class="keyword">if</span> emails:</span><br><span class="line">            errors.append(<span class="string">"That email has already been used"</span>)</span><br><span class="line">        <span class="keyword">if</span> pass_short:</span><br><span class="line">            errors.append(<span class="string">"Pick a longer password"</span>)</span><br><span class="line">        <span class="keyword">if</span> pass_long:</span><br><span class="line">            errors.append(<span class="string">"Pick a shorter password"</span>)</span><br><span class="line">        <span class="keyword">if</span> name_len:</span><br><span class="line">            errors.append(<span class="string">"Pick a longer user name"</span>)</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> len(errors) &gt; <span class="number">0</span>:</span><br><span class="line">            <span class="keyword">return</span> render_template(</span><br><span class="line">                <span class="string">"register.html"</span>,</span><br><span class="line">                errors=errors,</span><br><span class="line">                name=request.form[<span class="string">"name"</span>],</span><br><span class="line">                email=request.form[<span class="string">"email"</span>],</span><br><span class="line">                password=request.form[<span class="string">"password"</span>],</span><br><span class="line">            )</span><br><span class="line">        <span class="keyword">else</span>:</span><br><span class="line">            <span class="keyword">with</span> app.app_context():</span><br><span class="line">                user = Users(</span><br><span class="line">                    name=name.strip(),</span><br><span class="line">                    email=email_address.lower(),</span><br><span class="line">                    password=password.strip(),</span><br><span class="line">                )</span><br><span class="line">                db.session.add(user)</span><br><span class="line">                db.session.commit()</span><br><span class="line">                db.session.flush()</span><br><span class="line"></span><br><span class="line">                login_user(user)</span><br><span class="line"></span><br><span class="line">                <span class="keyword">if</span> config.can_send_mail() <span class="keyword">and</span> get_config(</span><br><span class="line">                    <span class="string">"verify_emails"</span></span><br><span class="line">                ):  <span class="comment"># Confirming users is enabled and we can send email.</span></span><br><span class="line">                    log(</span><br><span class="line">                        <span class="string">"registrations"</span>,</span><br><span class="line">                        format=<span class="string">"[&#123;date&#125;] &#123;ip&#125; - &#123;name&#125; registered (UNCONFIRMED) with &#123;email&#125;"</span>,</span><br><span class="line">                    )</span><br><span class="line">                    email.verify_email_address(user.email)</span><br><span class="line">                    db.session.close()</span><br><span class="line">                    <span class="keyword">return</span> redirect(url_for(<span class="string">"auth.confirm"</span>))</span><br><span class="line">                <span class="keyword">else</span>:  <span class="comment"># Don't care about confirming users</span></span><br><span class="line">                    <span class="keyword">if</span> (</span><br><span class="line">                        config.can_send_mail()</span><br><span class="line">                    ):  <span class="comment"># We want to notify the user that they have registered.</span></span><br><span class="line">                        email.sendmail(</span><br><span class="line">                            request.form[<span class="string">"email"</span>],</span><br><span class="line">                            <span class="string">"You've successfully registered for &#123;&#125;"</span>.format(</span><br><span class="line">                                get_config(<span class="string">"ctf_name"</span>)</span><br><span class="line">                            ),</span><br><span class="line">                        )</span><br><span class="line"></span><br><span class="line">        log(<span class="string">"registrations"</span>, <span class="string">"[&#123;date&#125;] &#123;ip&#125; - &#123;name&#125; registered with &#123;email&#125;"</span>)</span><br><span class="line">        db.session.close()</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> is_teams_mode():</span><br><span class="line">            <span class="keyword">return</span> redirect(url_for(<span class="string">"teams.private"</span>))</span><br><span class="line"></span><br><span class="line">        <span class="keyword">return</span> redirect(url_for(<span class="string">"challenges.listing"</span>))</span><br><span class="line">    <span class="keyword">else</span>:</span><br><span class="line">        <span class="keyword">return</span> render_template(<span class="string">"register.html"</span>, errors=errors)</span><br></pre></td></tr></table></figure>
<p>程序在判断用户名是否重复时,使用的用户名是用户直接Post过来的,而在存入数据库中的时候进行了strip操作.所以我们只要注册一个前面或后面加空格的admin账号即可绕过用户名重复的限制.</p>
<p>再来看一下找回密码的逻辑</p>
<p><a href="https://github.com/CTFd/CTFd/blob/fe85fdf1e5561e9f04c1c80c72e894dcd7ea3ad7/CTFd/auth.py#L95" target="_blank" rel="noopener">https://github.com/CTFd/CTFd/blob/fe85fdf1e5561e9f04c1c80c72e894dcd7ea3ad7/CTFd/auth.py#L95</a></p>
<figure class="highlight py"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@auth.route("/reset_password", methods=["POST", "GET"])</span></span><br><span class="line"><span class="meta">@auth.route("/reset_password/&lt;data&gt;", methods=["POST", "GET"])</span></span><br><span class="line"><span class="meta">@ratelimit(method="POST", limit=10, interval=60)</span></span><br><span class="line"><span class="function"><span class="keyword">def</span> <span class="title">reset_password</span><span class="params">(data=None)</span>:</span></span><br><span class="line">    <span class="keyword">if</span> data <span class="keyword">is</span> <span class="keyword">not</span> <span class="literal">None</span>:</span><br><span class="line">        <span class="keyword">try</span>:</span><br><span class="line">            name = unserialize(data, max_age=<span class="number">1800</span>)</span><br><span class="line">        <span class="keyword">except</span> (BadTimeSignature, SignatureExpired):</span><br><span class="line">            <span class="keyword">return</span> render_template(</span><br><span class="line">                <span class="string">"reset_password.html"</span>, errors=[<span class="string">"Your link has expired"</span>]</span><br><span class="line">            )</span><br><span class="line">        <span class="keyword">except</span> (BadSignature, TypeError, base64.binascii.Error):</span><br><span class="line">            <span class="keyword">return</span> render_template(</span><br><span class="line">                <span class="string">"reset_password.html"</span>, errors=[<span class="string">"Your reset token is invalid"</span>]</span><br><span class="line">            )</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> request.method == <span class="string">"GET"</span>:</span><br><span class="line">            <span class="keyword">return</span> render_template(<span class="string">"reset_password.html"</span>, mode=<span class="string">"set"</span>)</span><br><span class="line">        <span class="keyword">if</span> request.method == <span class="string">"POST"</span>:</span><br><span class="line">            user = Users.query.filter_by(name=name).first_or_404()</span><br><span class="line">            user.password = request.form[<span class="string">"password"</span>].strip()</span><br><span class="line">            db.session.commit()</span><br><span class="line">            log(</span><br><span class="line">                <span class="string">"logins"</span>,</span><br><span class="line">                format=<span class="string">"[&#123;date&#125;] &#123;ip&#125; -  successful password reset for &#123;name&#125;"</span>,</span><br><span class="line">                name=name,</span><br><span class="line">            )</span><br><span class="line">            db.session.close()</span><br><span class="line">            <span class="keyword">return</span> redirect(url_for(<span class="string">"auth.login"</span>))</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> request.method == <span class="string">"POST"</span>:</span><br><span class="line">        email_address = request.form[<span class="string">"email"</span>].strip()</span><br><span class="line">        team = Users.query.filter_by(email=email_address).first()</span><br><span class="line"></span><br><span class="line">        get_errors()</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> config.can_send_mail() <span class="keyword">is</span> <span class="literal">False</span>:</span><br><span class="line">            <span class="keyword">return</span> render_template(</span><br><span class="line">                <span class="string">"reset_password.html"</span>,</span><br><span class="line">                errors=[<span class="string">"Email could not be sent due to server misconfiguration"</span>],</span><br><span class="line">            )</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> <span class="keyword">not</span> team:</span><br><span class="line">            <span class="keyword">return</span> render_template(</span><br><span class="line">                <span class="string">"reset_password.html"</span>,</span><br><span class="line">                errors=[</span><br><span class="line">                    <span class="string">"If that account exists you will receive an email, please check your inbox"</span></span><br><span class="line">                ],</span><br><span class="line">            )</span><br><span class="line"></span><br><span class="line">        email.forgot_password(email_address, team.name)</span><br><span class="line"></span><br><span class="line">        <span class="keyword">return</span> render_template(</span><br><span class="line">            <span class="string">"reset_password.html"</span>,</span><br><span class="line">            errors=[</span><br><span class="line">                <span class="string">"If that account exists you will receive an email, please check your inbox"</span></span><br><span class="line">            ],</span><br><span class="line">        )</span><br><span class="line">    <span class="keyword">return</span> render_template(<span class="string">"reset_password.html"</span>)</span><br></pre></td></tr></table></figure>
<p>程序会根据你输入的邮箱发送相关账号更新信息到你邮箱中,而当你更新你的密码时,会从你访问的url获取data(你的假账号),并将它反序列化,根据序列化出来的对象的name值更新对应的账号(被覆盖的账号)密码</p>
<h2 id="利用方式"><a href="#利用方式" class="headerlink" title="利用方式"></a>利用方式</h2><ol>
<li>利用添加空格绕过限制来注册一个与受害者用户名相同的账号</li>
<li>生成忘记密码链接发送到自己的邮箱</li>
<li>将自己的账号的用户名改成与被攻击者不相同的用户名(可选)</li>
<li>用邮箱中收到的链接更改密码。</li>
<li>登录受害账户</li>
</ol>
<h2 id="参考资料"><a href="#参考资料" class="headerlink" title="参考资料"></a>参考资料</h2><p><a href="https://www.colabug.com/2020/0204/6940556/amp/" target="_blank" rel="noopener">CVE-2020-7245 CTFd v2.0.0 – v2.2.2 account takeover分析</a></p>

      
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              resultContent.innerHTML = '<div id="no-result"><i class="fa fa-search fa-5x" /></div>'
            } else if (resultItems.length === 0) {
              resultContent.innerHTML = '<div id="no-result"><i class="fa fa-frown-o fa-5x" /></div>'
            } else {
              resultItems.sort(function (resultLeft, resultRight) {
                if (resultLeft.searchTextCount !== resultRight.searchTextCount) {
                  return resultRight.searchTextCount - resultLeft.searchTextCount;
                } else if (resultLeft.hitCount !== resultRight.hitCount) {
                  return resultRight.hitCount - resultLeft.hitCount;
                } else {
                  return resultRight.id - resultLeft.id;
                }
              });
              var searchResultList = '<ul class=\"search-result-list\">';
              resultItems.forEach(function (result) {
                searchResultList += result.item;
              })
              searchResultList += "</ul>";
              resultContent.innerHTML = searchResultList;
            }
          }

          if ('auto' === 'auto') {
            input.addEventListener('input', inputEventFunction);
          } else {
            $('.search-icon').click(inputEventFunction);
            input.addEventListener('keypress', function (event) {
              if (event.keyCode === 13) {
                inputEventFunction();
              }
            });
          }

          // remove loading animation
          $(".local-search-pop-overlay").remove();
          $('body').css('overflow', '');

          proceedsearch();
        }
      });
    }

    // handle and trigger popup window;
    $('.popup-trigger').click(function(e) {
      e.stopPropagation();
      if (isfetched === false) {
        searchFunc(path, 'local-search-input', 'local-search-result');
      } else {
        proceedsearch();
      };
    });

    $('.popup-btn-close').click(onPopupClose);
    $('.popup').click(function(e){
      e.stopPropagation();
    });
    $(document).on('keyup', function (event) {
      var shouldDismissSearchPopup = event.which === 27 &&
        $('.search-popup').is(':visible');
      if (shouldDismissSearchPopup) {
        onPopupClose();
      }
    });
  </script>





  

  

  

  
  

  

  

  

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